This invention is directed to a method of optimizing tension distribution in the application of leg elastics to a garment. The method involves varying the number and position of feed nips and idler rolls and varying elongation of the elastic members.
Pant-like absorbent garments, such as adult incontinence wear, infant and children""s diapers, swim wear and training pants, typically include a pair of leg openings having an elastic portion around each leg opening. The elastic portions are intended to fit snugly around a wearer""s legs to prevent leakage from the garment. However, more tension is required in certain areas around the leg, such as in the crotch area, than in other areas around the leg, such as in the area away from the crotch.
Various technologies are known for applying leg elastics to such articles. For example, some technologies involve increasing spacing between elastic members at the crotch area around each leg opening. This type of spacing is the normal process fallout due to the correspondence between the angle of application and the spacing between the elastic members. More particularly, when the elastic members are applied to a garment in a machine direction, variations in the angle of application result in variations in spacing. When a device used to apply the elastic members aligns the elastic members in the crotch area in a row substantially perpendicular to the machine direction, as the elastic members are guided away from the crotch area, the angle between the row and the machine direction is closer to 0xc2x0, thereby resulting in wider spacing in the crotch area and narrower spacing in the area away from the crotch. Other technologies boast consistent spacing between elastic members around the entire leg opening. Some of the technologies mentioned, and others, include consistent tension among elastic members around the entire leg opening.
There is a need or desire for a process for optimizing gasketing pressure around the leg openings of pant-like absorbent garments to provide enhanced comfort, fit and containment about the leg openings of such garments.
It has been found that variations in tension among elastic members cause variations in gasketing pressure and can be optimized to provide enhanced comfort, fit and containment about the leg openings.
The present invention is directed to a method of applying leg elastics to pant-like absorbent garments using variable tension among the elastic members. The result is a garment with regions of customized higher tension for higher gasketing and regions of lower tension for greater comfort.
Apparatus that can be used for carrying out the invention includes a pivot arm that can be aligned substantially parallel or perpendicular to a substrate, or anywhere in between, with respect to the machine direction. The pivot arm can pivot from side to side across the substrate as the substrate travels through a pair of nip rolls in the machine direction. The pivot arm guides the elastic members as the elastic members are fed through a feed nip. The placement of the feed nip for the elastic members results in increased tension as the pivot arm moves the elastic members away from the feed nip. Conversely, as the pivot arm moves the elastic members toward the feed nip, the tension is reduced. The tension can be controlled in this manner such that higher tension can be applied in the desired area of the pant and lower tension can be applied in areas of the pant where less gasketing pressure is required.
In another embodiment of the invention, separate feed nips are provided for each elastic member. As a result, the tension profile of each elastic member can be different. The placement of the feed nip relative to the corresponding elastic guide at any given pivot arm position determines the tension profile in the elastic member, even if the feed nips are driven at the same constant speed.
In a further embodiment of the invention, idler rolls are located in various positions. As a result, the tension profile of each elastic member can be different. More specifically, a strategically placed elastic feed nip and a corresponding idler roll change the stretching amount of each individual elastic member such that a different and even opposite tension gradient can be placed on members that are side by side in the product composite.
In yet another embodiment of the invention, an idler roll on a shaft connected to a rotating wheel is used to control elongation of the elastic members. Virtually any type of tension profile can be created with this method.
With the foregoing in mind, it is a feature and advantage of the invention to provide a method of applying leg elastics to an absorbent garment resulting in optimized performance of the leg elastics in terms of comfort, fit and containment.
It is another feature and advantage of the invention to provide a method of tailoring leg elastic tension in an absorbent garment to fit a wearer""s body.